Spin weld part and spin welding method

ABSTRACT

An object is to provide a spin welding component that has a simple configuration of a welding surface and provides enhanced welding strength. A spin welding component  1  includes a shaft portion  2  formed in an approximately columnar shape, a flange portion  3  extended outward from below the shaft portion  2  to be formed in a disk-like shape, and an opening  4  formed by opening part of a bottom face of the flange portion  3 . A molten resin  9  as molten material is applied on the bottom face. High-speed rotation causes the molten resin  9  to be melted by the frictional heat, and part of the molten resin  9  enters the opening  4  to be welded.

TECHNICAL FIELD

The present invention relates to a welding component as a mountingmember used for spin welding that melts and bonds a welding material bythe frictional heat caused by rotation.

BACKGROUND ART

Patent Literature 1 has been known as the prior art with regard to spinwelding. This aims to reduce a so-called “through transfer phenomenon”that causes a bent or wrinkle on a mounting substrate 6 in the processof fixing a fixture 2 to the mounting substrate 6 by rotational welding.In a rotational welding resin member of Patent literature 1 having acolumnar portion and a disk-shaped flange portion integrally provided atone end of the columnar portion, the wall thickness of the flangeportion is gradually decreased from the center toward the outercircumference.

CITATION LIST Patent Literature

PTL 1: JP H04-026297B

SUMMARY Technical Problem

There is, however, still a room for improvement with regard to thetechnique of enhancing the strength of spin welding or more specificallywith regard to good balance between the manufacturing cost of a weldingcomponent and the welding strength. For example, when a mounting bracketis spin-welded to a base member, the molten material is concentrated inthe center, so that the mounting bracket rises from the base member.This causes the problems of failing to provide the sufficient weldingstrength, the good appearance and the high dimensional accuracy (asshown in FIG. 3).

An object of the invention is thus to provide a spin welding componentthat has a simple configuration of a welding surface and providesenhanced welding strength, good appearance and high dimensionalaccuracy.

Solution to Problem

By taking into account the above object, according to one aspect of theinvention, there is provided a spin welding component comprising a mainbody including a resin; and an opening in a concave shape provided atcenter of a bottom of the main body. It is preferable that the main bodyhas a flange portion integrally provided with a shaft portion and thatthe opening is formed on the shaft portion. The opening preferably has acircular bottom face.

The volume of the opening is preferably set according to the amount ofthe molten resin of at least the spin welding component. This ratio maydiffer, for example, according to the material of the spin weldingcomponent. It is preferable that the ratio of the amount of molten resinto the volume of opening is basically 1 to 1. The ratio of amount ofmolten resin:volume of the opening may be 1:0.7 to 1.3. It is generallypreferable that the volume of the opening is greater than the amount ofthe molten resin. The less volume of the opening, on the contrary,enables the molten resin to be pressed downward by the spin weldingcomponent. For example, when the volume of the opening is 0.8 relativeto the amount of molten resin=1, a cover may be placed over the moltenresin to apply a pressure. This ensures favorable bonding. The bondingstrength may be increased to 1.4 to 1.6 times. This configurationprevents a pressure of more than necessity from being applied betweenthe spin welding component and the base member. This accordinglysuppresses deterioration of the appearance by the molten resin or bydeformation of the spin welding component and the base member andensures the dimensional accuracy.

It is preferable that the bottom face of the spin welding component iswelded to the base member via the resin molten by spinning. When thespin welding component and the base member are made of the samematerial, the material may be melted. When the spin welding componentand the base member are made of different materials, these materials maybe tangled or dissolved. A welding resin material of the same materialor a different material may be provided on the bottom face of the mainbody.

According to another aspect of the invention, there is provided a spinwelding method comprising: rotating the spin welding component of theabove aspect that is placed on a base member to be in close contact withthe base member; melting the spin welding component by frictional heatbetween the base member and the spin welding component caused by therotating; causing molten resin to be concentrated in a center and flowinto the opening by the rotating such that the spin welding componentpresses the molten resin downward; and solidifying the molten resinflowing into the opening to weld the spin welding component with thebase member.

The material of the spin welding component and the material of the basemember may be selected adequately. For example, the material of the spinwelding component may be polyester, polyethylene or polypropylene, andthe material of the base member may be kenaf and/or 50% glass and 50%polypropylene.

In the spin welding component of the above aspect, the opening may beformed in a reverse concave sectional shape having an inner ceiling. Themolten resin may be solidified in the state that the molten resin is incontact with the inner ceiling or in the state that the molten resin isnot in contact with the inner ceiling.

The bottom preferably has an approximately circular shape, since this issuitable for spin welding. This is, however, not essential.

In the bottom of the spin welding component of the above aspect, theopening denotes a cavity in a reverse concave sectional shape having anopen bottom face. An inner ceiling may be formed in an upper portion ofthe cavity or may not be formed. The opening is formed in, for example,a circular shape, but may be formed in another shape such as arectangular shape or a hexagonal shape.

The shaft portion and the flange portion of the main body may be formedintegrally or may be formed separately and subsequently integrated.

Advantageous Effects of Invention

The spin welding component according to the above aspect of theinvention has enhanced welding strength. The configuration of the spinwelding component prevents a pressure of more than necessity from beingapplied between the spin welding component and a welded member such as abase member. This accordingly suppresses deformation of the spin weldingcomponent and the base member by the molten resin and ensures the goodappearance in the mounted state and the improved dimensional accuracy.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a downward perspective view illustrating a spin weldingcomponent 1 according to Embodiment 1 of the invention; FIG. 1(b) is anupward perspective view illustrating the spin welding component 1 ofEmbodiment 1; FIG. 1(c) is a front view illustrating the spin weldingcomponent 1 of Embodiment 1, wherein molten resin 9 is omitted from theillustration;

FIG. 2 is a schematic sectional view illustrating the state that thespin welding component 1 of Embodiment 1 is welded to a base member 8;

FIG. 3 is a schematic sectional view illustrating the state that aconventional spin welding component 11 is welded to a base member 18;

FIG. 4(a) is a downward perspective view illustrating a spin weldingcomponent 101 according to Embodiment 2 of the invention; FIG. 4(b) isan upward perspective view illustrating the spin welding component 101of Embodiment 2; FIG. 4(c) is a front view illustrating the spin weldingcomponent 101 of Embodiment 2, wherein molten resin 109 is omitted fromthe illustration;

FIGS. 5(a), 5(b) and 5(c) are diagrams illustrating modifications of thespin welding component 101 of Embodiment 2;

FIG. 6 is a schematic sectional view illustrating the state that thespin welding component 101 of Embodiment 2 is welded to a base member108;

FIG. 7(a) is a downward perspective view illustrating a spin weldingcomponent 201 according to Embodiment 3 of the invention; FIG. 7(b) isan upward perspective view illustrating the spin welding component 201of Embodiment 3; FIG. 7(c) is a front view illustrating the spin weldingcomponent 201 of Embodiment 3, wherein molten resin 209 is omitted fromthe illustration;

FIG. 8(a) is a schematic sectional view illustrating the state that aspin welding component 301 according to Embodiment 4 is mounted on abase member 308; and FIG. 8(b) is a schematic sectional viewillustrating the state that a spin welding component 401 according toEmbodiment 5 is mounted on a base member 408; and

FIG. 9 is a graph showing a relationship between the recessed area andthe strength in the case where spin welding components as Examples ofthe invention are thermally welded to a base member.

DESCRIPTION OF EMBODIMENTS

A spin welding component 1 according to Embodiment 1 of the invention isdescribed with reference to FIGS. 1 and 2. The spin welding component 1includes has a main body including a shaft portion 2 formed in anapproximately columnar shape and a flange portion 3 extended outwardfrom below the shaft portion 2 to be formed in a disk-like shape asshown in FIGS. 1(a) to 1(c). The spin welding component 1 also includesan opening 4 formed by opening the entirety or part of a bottom face ofthe shaft portion 2.

The configuration of the spin welding component 1 is described morespecifically with reference to FIGS. 1(a) to 1(c). The spin weldingcomponent 1 is a plastic molded part produced by integrally molding theshaft portion 2 and the flange portion 3. The shaft portion 2 is formedin a cap-like shape including a cylindrical body 5 in an approximatelycylindrical shape and an upper plate 6 integrally provided on thecylindrical body 5. The flange portion 3 is a ring-shaped plate memberthat is extended radially outward from the circumference of a lower endof the shaft portion 2 as the base. The opening 4 is formed at thecenter of a bottom of the cylindrical body 5 to define an inner cavityof the shaft portion 2 and is recessed upward from a bottom face of thespin welding component 1. The bottom of the cylindrical body 5 isconnected with the inner circumference of the flange portion 3, and thecylindrical body 5 is extended upward from the flange portion 3. Thecylindrical body 5 has diameter expanded downward but may have a fixeddiameter. The upper plate 6 has an upper hole 7 formed in its center.This is, however, not essential but is an example of the productconfiguration, and the upper hole 7 may be omitted. The spin weldingcomponent 1 may have an optional configuration suitable for spin weldingor an optional configuration required according to the specification ofa final product.

Available examples of the material used for the spin welding component 1include thermoplastic resins such as polyester, polyethylene,polypropylene, polystyrene, polyvinyl chloride, acrylic resin,acrylonitrile-butadiene-styrene resin, polyethylene terephthalate,nylon, polyamide, polycarbonate and polyacetal, thermosetting resinssuch as phenolic resin, epoxy resin and melamine resin and compositematerials such as glass fiber-reinforced plastic and carbonfiber-reinforced plastic.

Available examples of the material for a welded member to which the spinwelding component 1 is mounted include thermoplastic resins such aspolyester, polyethylene, polypropylene, polystyrene, polyvinyl chloride,acrylic resin, acrylonitrile-butadiene-styrene resin, polyethyleneterephthalate, nylon, polyamide, polycarbonate and polyacetal andcomposite materials of these thermoplastic resins with glass fiber,carbon fiber or kenaf.

According to this embodiment, the spin welding component 1 is made ofpolypropylene. The flange portion 3 has a diameter of 40 mmφ, and theopening 4 has a diameter of 22 mmφ. A base member 8 as the welded memberis a plate-like member made of a composite material consisting of 50%kenaf and 50% polypropylene.

The following describes a method of welding the spin welding component1. The spin welding component 1 is fastened above the base member 8 asthe welded member via a jig (not shown) in a spin welding machine (notshown). As shown in FIG. 2(a), on completion of setting the respectivecomponent and member, the spin welding component 1 is moved downwardwhile rotating at high speed by the spin welding machine (not shown).The spin welding component 1 comes into contact with the base member 8and is subsequently kept in close contact with the base material 8 underapplication of a downward load. When the spin welding component 1rotates at high speed at a fixed point, the spin welding component 1 andthe base material 8 are melted by the frictional heat. The molten resinis flowed toward the center of the opening 4 by the rotation and issolidified to weld the spin welding component 1 to the base member 8 asshown in FIG. 2(b). The spin welding component 1 may be used forautomobile interior parts and may also be favorably used for small partssuch as various brackets.

The following describes the functions and advantageous effects of thespin welding component 1. In the mounted state of the spin weldingcomponent 1 shown in FIG. 2(b), the spin welding component 1 is weldedto the base material 8 in areas A on the lower face of the flange 3.This is compared with a conventional spin welding component 11 withoutthe opening 4 with reference to FIGS. 3(a) and 3(b).

The conventional spin welding component 11 has the similar configurationand the similar dimensions except the opening 4 and is made of thesimilar material. Spin welding of this conventional spin weldingcomponent 11 causes a molten resin 19 concentrated at the center to besolidified as shown in FIG. 3.

The principle of solidifying the molten resin 19 concentrated at thecenter has not been elucidated. The results of a considerable number ofexperiments under the above conditions, however, indicate thisphenomenon. Solidification of the molten resin 19 concentrated at thecenter causes the spin welding component 11 to be welded only in an areaB but not in areas A. The spin welding component 11 accordingly risesfrom the base member 18. This causes a variation in mounting accuracyand a variation in welding strength and reduces the welding strength.This also causes deterioration of the appearance.

In the case of the spin welding component 1 according to Embodiment 1 ofthe invention, on the other hand, the molten resin that is melted duringspin welding is partly flowed into the opening 4, so that the spinwelding component 1 is welded in the areas A, i.e., in the entre bottomface of the flange portion 3. This provides the higher welding strengththan the conventional spin welding component. This also suppresses arise of the member in the welded state and stably provides the desiredmounting accuracy and the desired welding strength.

A spin welding component 101 according to Embodiment 2 of the inventionis described with reference to FIGS. 4 to 6. The like components tothose of Embodiment 1 are expressed by the like numerals to those ofEmbodiment 1 in their 100s and are not specifically described. As shownin FIGS. 4(a) to 4(c), like the spin welding component 1, the spinwelding component 101 includes a shaft portion 102 formed in anapproximately columnar shape, a flange portion 103 extended outward frombelow the shaft portion 102 to be formed in a disk-like shape, and anopening 104 formed by opening part of a bottom face of the flangeportion 103. The opening 104 is formed in a reverse concave sectionalshape having a less opening height than that of the spin weldingcomponent 1 and has an inner ceiling 110.

The opening 104 of Embodiment 2 has the inner ceiling 110 provided toclose the upper portion inside of the shaft portion 102 and isaccordingly formed as a cavity in an approximately short cylindricalshape having the reverse concave sectional shape. Some examples ofproviding the inner ceiling 110 are shown in FIG. 5. FIG. 5(a)illustrates the inner ceiling 110 that is an inner configuration formedby integrally filling the cavity other than the opening 104 to be solidwith molding the spin welding component 101. FIG. 5(b) illustrates aninner ceiling 110′ provided to part the cavity in a shaft portion 102′.FIG. 5(c) illustrates a configuration obtained by filling the cavity ofa shaft portion 102″ in a spin welding component having the similarconfiguration to that of the spin welding component 1 of Embodiment 1with a filling member 111. The filling member 111 may be made of thesame material as or may be made of a different material from thematerial of the spin welding component 1. For example, the material maybe a fiber composite material or a porous material to provide thewelding strength with the molten resin.

The spin welding component 101 is set in a spin welding machine (notshown) (shown in FIG. 6(a)) and is spin-welded to a base member 108(shown in FIG. 6(b)), like Embodiment 1.

The following describes the functions and advantageous effects of thespin welding component 101. In the mounted state of the spin weldingcomponent 101 shown in FIG. 6(b), molten resin 109 concentrated in theopening 104 like Embodiment 1 is trapped by the inner ceiling 110 and issolidified in the state that the molten resin 109 is in contact with theinner ceiling 110. The spin welding component 101 is accordingly weldedin an area B as well as in areas A like Embodiment 1.

This welds the entire bottom face of the spin welding component 101 andthereby provides the stronger welding than Embodiment 1. Welding theentire bottom face reduces a variation in welding strength of an actualproduct relative to a designed strength. There is accordingly no need toapply a load of more than necessity for spin welding. This suppressesdeformation and damaged appearance of the spin welding component 101 andthe base member 108 and readily ensures the dimensional accuracy.

With regard to the spin welding component 101, it is preferable to usethe same type of thermoplastic resin or thermoplastic resin-containingcomposite material for the shaft portion 102, the flange portion 103,the molten resin 109 and the base member 108. Even when differentmaterials are used, the molten resin 109 comes in close contact with theshaft portion 102, the flange portion 103 and the base member 108. Thisenhances the strength.

A spin molding component 201 according to Embodiment 3 of the inventionis described with reference to FIG. 7. The like components to those ofEmbodiment 2 are not specifically described. As shown in FIGS. 7(a) to7(c), the spin molding component 201 is formed in an approximatelycylindrical shape as a whole without a flange portion and includes anopening 204 formed on its bottom face in a reverse concave sectionalshape with an inner ceiling 210. The spin welding component 201 ofEmbodiment 3 has the similar functions and advantageous effects to thoseof Embodiment 2.

A spin molding component 401 according to Embodiment 4 of the inventionis described with reference to FIG. 8(a). The like components to thoseof Embodiments 1 to 3 are not specifically described. As shown in FIG.8(a), the spin welding component 401 has a welding resin film 409 in acircular shape applied between a shaft portion 402 and a bottom face ofa flange portion 403. The welding resin 409 may be applied to cover anopening 404 or may be applied not to cover the opening 404. The weldingresin 409 as the molten material is applied in advance on the bottomface of the spin welding component 1, prior to spin welding. The spinwelding component 401 of Embodiment 4 has the similar functions andadvantageous effects to those of Embodiments 1 to 3.

It is preferable to use the same type of thermoplastic resin orthermoplastic resin-containing composite material as that of the spinwelding component 401 for the welding resin 409 as the molten material.This is, however, not essential and another material may be used.According to this embodiment, the welding resin 409 is made of acomposite material consisting of 50% kenaf and 50% polypropylene like abase member 408 and is applied on the bottom face of the spin weldingcomponent 401.

The following describes a method of welding the spin welding component401. The spin welding component 401 is fastened above the base member408 as the welded member via a jig (not shown) in a spin welding machine(not shown). As shown in FIG. 2(a), on completion of setting therespective component and member, the spin welded component 1 is moveddownward while rotating at high speed by the spin welding machine (notshown). The spin welding component 401 comes into contact with the basemember 408 and is subsequently kept in close contact with the basematerial 408 under application of a downward load. When the spin weldingcomponent 401 rotates at high speed at a fixed point, the welding resin9 is melted by the frictional heat. The melted welding resin 409 isflowed into the opening 404 by the rotation and is solidified to weldthe spin welding component 401 with the base member 408.

A spin welding component 501 according to Embodiment 5 of the inventionis described with reference to FIG. 8(b). The like components to thoseof Embodiment 4 are not specifically described. This spin weldingcomponent 5 has an opening 501 of reduced volume. The configuration ofEmbodiment 5 has the similar functions and advantageous effects to thoseof Embodiment 4. Additionally, the limited volume of the opening 501 hasthe effect of pressing the molten resin downward during thermal welding.

FIG. 9 is a graph showing the relationship of the strength to theconcave area of the opening 4, 104, 204, 401 or 501. The concave area(%) herein denotes an area ratio in percentage of the area of the bottomface of the opening 4, 104, 204, 401 or 501 (cavity) to the area of thebottom face of the spin welding component 1, 101, 201, 401 or 501 (areaof the ring shape, i.e., the bottom area where the molten resin ispresent). The entire diameter of the spin welding component 1, 101, 201,401 or 501 is in the range of 20 mm to 40 mm. Type A showsconfigurations with an opening, and type B shows configurations withoutan opening in the bottom face. The concave area of 5 to 35% of thewelding area is likely to increase the strength. The welding strength isincreased to about 1.5 times at most.

The rotation speed of the spin welding component 1, 101, 201, 301, 401or 501 may be about 2500 rpm. The rotation speed, however, depends onthe material of the resin and the configuration of the spin weldingcomponent. The rotation speed is accordingly not limited to thisnumerical value but may be selected in an adequate range.

The invention is not limited to the above embodiments but variousmodifications, changes and additions may be made to the embodimentswithout departing from the scope of the invention. Such modifications aswell as their equivalents are also included in the scope of theinvention.

REFERENCE SIGNS LIST

-   -   1, 101, 201 spin welding component    -   2, 102 shaft portion    -   3, 103 flange portion    -   4, 104 opening    -   110 inner ceiling    -   8, 108 base member    -   9, 109 molten resin

1. A spin welding component, comprising: a main body including a resin;and an opening in a concave shape provided at center of a bottom of themain body.
 2. The spin welding component according to claim 1, whereinthe main body has a flange portion integrally provided with a shaftportion, and the opening is formed on the shaft portion.
 3. The spinwelding component according to either claim 1 or claim 2, wherein awelding resin material is provided on a bottom face of the main body. 4.A spin welding method, comprising: rotating the spin welding componentaccording to claim 1 that is in close contact with a base member;melting the spin welding component by frictional force between the basemember and the spin welding component caused by the rotating; causingmolten resin to flow into the opening by the rotating; and solidifyingthe molten resin flowing into the opening to weld the spin weldingcomponent with the base member.